A field emission device (FED) comprises a cathode which may be conically shaped or have some other suitable form to provide for a point from which electrons are emitted upon application of an electric field. An anode is placed near the tip of the cathode, but separated from the cathode by a vacuum. A FED array includes field emission devices arranged in a series of columns and rows. Each column and row interface defines a pixel having an associated parasitic capacitance. Current display applications demand thinner, lighter, brighter, and less expensive FED arrays that consume less power.
To activate a pixel, a row driver supplies a voltage to each gate in a row of the FED array. A column driver supplies a voltage signal to each cathode in a column of the FED array. This forms an electric field between each cathode and gate at the pixel of the designated column and row. The magnitude of this electric field across the cathode and gate of each pixel controls the emission of electrons from each cathode of a given pixel. An anode power supply provides a global voltage to each pixel in the FED array, creating another electric field between the anode and the cathode of each pixel. The magnitude of this electric field controls the intensity of the light emitted at each pixel.
Typically, a column driver supplies a pulse-width modulated voltage signal starting at a low state and transitioning to a high state later in the frame of the signal, depending on the brightness desired at each pixel. At the beginning of the next frame of the signal, the signal is returned to a low state. Each state transition from high to low discharges the parasitic capacitance associated with each pixel of the FED array. Thereafter, each state transition from low to high recharges these capacitances. Discharging and recharging the capacitances of the FED array causes undesired power dissipation proportional to the frequency of the column driver output signal, pursuant to the equation P=1/2CV.sup.2 f.
One effort to minimize the power dissipation of FED arrays employs energy recovery circuits. Another technique supplies an analog voltage signal to each column of the array. However, both of these methods require additional components and complexity. These additional components are expensive and occupy valuable packaging space. The resulting FED array is larger and consumes more power than desired or feasible.